U.S. patent application number 12/759085 was filed with the patent office on 2010-10-21 for controller for fuel pump.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Naoki YOSHIUME.
Application Number | 20100268441 12/759085 |
Document ID | / |
Family ID | 42981632 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100268441 |
Kind Code |
A1 |
YOSHIUME; Naoki |
October 21, 2010 |
CONTROLLER FOR FUEL PUMP
Abstract
When a starter is started, a start-control duration time is
established based on a fuel pressure at engine starting and a
target fuel pressure. The start-control duration time corresponds
to a duration after the engine is started until a difference
between an actual fuel pressure in an accumulator and a target fuel
pressure becomes lower than a specified value in a case that the
fuel pump discharges the fuel at a maximum rate. A fuel pump
discharges the fuel at the maximum rate during the estimated
start-control duration time.
Inventors: |
YOSHIUME; Naoki;
(Takahama-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
42981632 |
Appl. No.: |
12/759085 |
Filed: |
April 13, 2010 |
Current U.S.
Class: |
701/103 ;
123/447 |
Current CPC
Class: |
F02D 41/062 20130101;
F02M 59/447 20130101; F02D 41/3845 20130101; F02M 59/34 20130101;
F02M 63/0265 20130101; F02D 2200/0602 20130101 |
Class at
Publication: |
701/103 ;
123/447 |
International
Class: |
F02D 41/30 20060101
F02D041/30; F02M 63/00 20060101 F02M063/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2009 |
JP |
2009-98822 |
Claims
1. A controller for a fuel pump applied to a fuel injection system
for an internal combustion engine, which includes an accumulator
accumulating a fuel at high pressure, a fuel pump supplying the
fuel to the accumulator from a fuel tank and a fuel pressure sensor
detecting a fuel pressure in the accumulator, the controller
comprising: an estimation means for estimating a start-control
duration time at an engine starting time, the start-control
duration time corresponding a duration after the engine is started
until a difference between an actual fuel pressure in the
accumulator and a target fuel pressure becomes lower than a
specified value in a case that the fuel pump discharges the fuel at
a maximum rate; and a start-control means for controlling the fuel
pump in such a manner as to discharge the fuel at the maximum rate
during the estimated start-control duration time.
2. A controller for a fuel pump according to claim 1, wherein the
fuel pump suctions and discharges the fuel in accordance with a
rotation of a crankshaft of the engine, and the estimation means
estimates the start-control duration time based on a number of
discharge of the fuel pump at the maximum rate after an engine
start requirement is generated until the difference between an
actual fuel pressure in the accumulator and the target fuel
pressure becomes lower than the specified value.
3. A controller for a fuel pump according to claim 1, wherein the
fuel injection system includes a cam angle sensor detecting a
rotational angle of a camshaft of the engine and a crank angle
sensor detecting a rotational angle of a crankshaft of the engine,
the fuel pump suctions and discharges the fuel in accordance with a
rotation of the crankshaft or the crankshaft, and the start-control
means determines that the estimated start-control duration time
terminates when a number of output of the cam angle sensor or the
crank angle sensor reaches a specified value determined by the
estimation means after an engine start requirement is
generated.
4. A controller for a fuel pump according to claim 1, further
comprising: a detecting means for detecting at least one of a
battery voltage and the coolant temperature, wherein the fuel pump
is driven by a driving force transmitted from a crankshaft of the
engine, and suctions and discharges the fuel in accordance with a
rotation of the crankshaft, and the estimation means estimates the
start-control duration time in consideration of a detection value
of the detection means.
5. A controller for a fuel pump according to claim 1, wherein the
fuel pump suctions and discharges the fuel in accordance with a
rotation of a camshaft or crankshaft of the engine, the fuel pump
is provided with a normally open valve which fluidly connects or
disconnects a fuel inlet port and a pump chamber in which the fuel
is pressurized, the fuel pump of which discharge rate is adjusted
according to an energization timing of the normally open valve, and
the start-control means energizes the normally open valve during
the estimated start-control duration time.
6. A controller for a fuel pump according to claim 1, wherein the
fuel injection system includes a cam angle sensor detecting a
rotational angle of a camshaft of the engine and a crank angle
sensor detecting a rotational angle of a crankshaft of the engine,
the fuel pump suctions and discharges the fuel in accordance with a
rotation of a camshaft and crankshaft of the engine, the fuel pump
is provided with a normally open valve which fluidly connects or
disconnects a fuel inlet port and a pump chamber in which the fuel
is pressurized, the fuel pump of which discharge rate is adjusted
according to an energization timing of the normally open valve, and
the start-control means energizes the normally open valve based on
at least one of the cam angle sensor and the crank angle sensor
during a time period which includes a start timing of a discharge
stroke of the fuel pump and which is shorter than one cycle of a
suction stroke and discharge stroke of the fuel pump.
7. A controller for a fuel pump according to claim 1, wherein the
fuel pump is provided with a normally close valve which fluidly
connects or disconnects a fuel inlet port and a pump chamber in
which the fuel is pressurized, the fuel pump of which discharge
rate is adjusted according to an energization timing of the
normally open valve, and the start-control means deenergizes the
normally close valve during the estimated start-control duration
time.
8. A controller for a fuel pump according to claim 5, wherein the
estimation means sets an upper limit of a continuous energization
period of the normally open valve.
9. A controller for a fuel pump according to claim 1, wherein the
estimation means estimates the start-control duration time during
which at least one discharge of the fuel pump is conducted.
10. A controller for a fuel pump according to claim 9, wherein the
fuel injection system further includes: a fuel injector injecting a
fuel supplied from the accumulator; and a diagnosis means for
performing a diagnosis whether a defect exists in a fuel supply
pipe between the fuel tank and the fuel injector, the fuel
injector, or the fuel pressure sensor.
11. A controller for a fuel pump according to claim 1, wherein the
fuel pump is provided with a valve which fluidly connects or
disconnects a fuel inlet port and a pump chamber in which the fuel
is pressurized, the fuel pump of which discharge rate is adjusted
according to an energization timing of the valve, further
comprising: an identification means for identifying whether the
fuel pump is at a suction stroke or a discharge stroke; and a
control switching means for controlling an energization timing of
the valve in such a manner that that the fuel pressure detected by
the fuel pressure sensor agrees with the target fuel pressure after
the identification means has identified whether the fuel pump is at
a suction stroke or a discharge stroke.
12. A controller for a fuel pump according to claim 11, wherein the
control switching means controls an energization timing of the
valve based an integral value of a difference between the fuel
pressure detected by the fuel pressure sensor and the target fuel
pressure.
13. A controller for a fuel pump applied to a fuel injection system
for an internal combustion engine, which includes an accumulator
accumulating a fuel at high pressure, and a fuel pump supplying the
fuel to the accumulator from a fuel tank, the controller
comprising: an estimation means for estimating a start-control
duration time at an engine starting time, the start-control
duration time corresponding a duration after the engine is started
until a difference between an actual fuel pressure in the
accumulator and the target fuel pressure becomes lower than a
specified value in a case that the fuel pump discharges the fuel at
a maximum rate; and a start-control means for controlling the fuel
pump in such a manner as to discharge the fuel at the maximum rate
during the estimated start-control duration time after an engine
start requirement is generated.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application No.
2009-98822 filed on Apr. 15, 2009, the disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a controller for a fuel
pump which is applied to a fuel injection system having an
accumulator accumulating high-pressure fuel supplied from the fuel
pump and a fuel pressure detecting means for detecting a fuel
pressure in the accumulator.
BACKGROUND OF THE INVENTION
[0003] It is known that a controller for a fuel pump is applied to
a fuel injection system of a direct injection engine. The fuel
injection system includes an accumulator accumulating a
high-pressure fuel and a fuel pump supplying the high-pressure fuel
to the accumulator. The fuel pump is driven by a pump cam rotating
in synchronization with a camshaft of the engine. A discharge rate
of the fuel pump is adjusted by controlling an energization of a
solenoid installed in the fuel pump. Specifically, a cylinder
identification is conducted to determine whether the fuel pump is
at a suction stroke or at a discharge stroke. After the cylinder
identification, a required discharge rate of the fuel pump is
computed based on a proportional term and an integral term of a
deviation between an actual fuel pressure and a target fuel
pressure so that the actual fuel pressure in the accumulator agrees
with the target fuel pressure. Based on this required discharge
rate, an energization timing of the solenoid is computed. Thereby,
the actual fuel pressure is controlled to agree with the target
fuel pressure, which is set at each engine driving condition, and
an exhaust characteristic is improved.
[0004] When the engine is stopped, the actual fuel pressure in the
accumulator gradually decreases. Thus, in a case that the engine
has been stopped for a long time period, the actual fuel pressure
in the accumulator decreases excessively relative to the target
fuel pressure. When the engine is re-started, it is required that
the actual fuel pressure is increased to the target fuel pressure
immediately. However, since the actual fuel pressure can not be
feedback controlled during a period from the engine start until the
cylinder identification, an increase in the actual fuel pressure is
delayed, so that the exhaust characteristic is deteriorated.
[0005] Conventionally, as shown in JP-2008-223528A (US
2008/0216797A1), the solenoid of the fuel pump is continuously
energized from the engine start until the completion of the
cylinder identification so that the discharge rate of the fuel pump
is made maximum, whereby the increase in the actual fuel pressure
is expedited and the deterioration in the exhaust characteristic is
restricted. A control in which the discharge rate of the fuel pump
is made maximum is referred to as a full discharge control,
hereinafter. Also, Japanese patent No. 4110065 (US 2005/0045158A1)
shows a control method of a solenoid of a fuel pump.
[0006] In view of controlling the actual fuel pressure, a
completion timing of the cylinder identification is not always
appropriate as a completion timing of the fuel discharge control.
For example, in a case that the actual fuel pressure is lower than
the target fuel pressure at the completion timing of the cylinder
identification, the integral term of the feedback control becomes
excessively large due to an increase in deviation between the
actual fuel pressure and the target fuel pressure. It is likely
that an overshoot may occur, in which the actual fuel pressure
continues to increase even after the actual fuel pressure reaches
the target fuel pressure. In a case that the actual fuel pressure
is greater than the target fuel pressure at the completion timing
of the cylinder identification, it means that the completion timing
of the cylinder identification is late as the completion timing of
the full discharge control.
SUMMARY OF THE INVENTION
[0007] The present invention is made in view of the above matters,
and it is an object of the present invention to provide a
controller for a fuel pump, which is able to set an appropriate
completion timing of a full discharge control in which a discharge
rate of the fuel pump is made maximum at starting of engine.
[0008] According to the present invention, a controller for a fuel
pump is applied to a fuel injection system for an internal
combustion engine. The fuel injection system includes an
accumulator accumulating a fuel at high pressure, a fuel pump
supplying the fuel to the accumulator from a fuel tank, and a fuel
pressure sensor detecting a fuel pressure in the accumulator. The
controller includes: an estimation means for estimating a
start-control duration time after the engine is started until a
difference between an actual fuel pressure in the accumulator and
the target fuel pressure becomes lower than a specified value in a
case that the fuel pump discharges the fuel at a maximum rate; and
a start-control means for controlling the fuel pump in such a
manner as to discharge the fuel at the maximum rate during the
estimated start-control duration time.
[0009] A fuel quantity necessary for increasing an actual fuel
pressure to a target fuel pressure is computed based on a
difference between the actual fuel pressure and the target fuel
pressure and a volume of a pipe between the fuel pump and the
accumulator. A start-control duration time after the engine is
started until the difference between the actual fuel pressure and
the target fuel pressure becomes lower than a specified value can
be estimated with high accuracy. During this start-control duration
time, the fuel pump is controlled in such a manner as to discharge
the fuel at a maximum rate. Thus, according to the present
invention, a completion timing of a period in which the fuel pump
discharges the fuel at the maximum rate can be appropriately
established.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Other objects, features and advantages of the present
invention will become more apparent from the following description
made with reference to the accompanying drawings, in which like
parts are designated by like reference numbers and in which:
[0011] FIG. 1 is a schematic view showing an entire structure of a
fuel injection system according to a first embodiment;
[0012] FIG. 2 is a block diagram showing a fuel pressure control in
a delivery pipe according to the first embodiment;
[0013] FIG. 3 is a flow chart showing a procedure of a
start-control according to the first embodiment;
[0014] FIGS. 4A to 4C are time charts showing a start-control
according to the first embodiment;
[0015] FIGS. 5A to 5F are time charts showing a start-control
according to a second embodiment;
[0016] FIGS. 6A to 6C are time charts showing a start-control
according to a third embodiment; and
[0017] FIG. 7 is a block diagram showing a fuel pressure control in
a delivery pipe according to a fourth embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
First Embodiment
[0018] Referring to drawings, a first embodiment of a controller
for a fuel pump which is applied to a fuel injection system of a
direct injection gasoline engine will be described hereinafter.
[0019] FIG. 1 shows an entire structure of a fuel injection system
according to a first embodiment.
[0020] A fuel stored in a fuel tank 10 is pumped up by an electric
feed pump 14 through a low-pressure pipe 12. The pumped-up fuel is
adjusted to a low-pressure fuel by a low-pressure regulator 16 and
is supplied to a high-pressure fuel pump 18.
[0021] The high-pressure fuel pump 18 has a cylinder 20, a plunger
22 reciprocating in the cylinder 20, a pump chamber 24 defined by
an inner wall surface of the cylinder 20 and the plunger 22, a
spill valve 28 connecting or disconnecting an inlet port 26 and the
pump chamber 24, and a discharge valve 32 provided between an
outlet port 30 and the pump chamber 24.
[0022] The spill valve 28 is biased to a close-position by a
valve-closing spring 34. A valve-opening spring 40 biases the spill
valve 28 in a valve-opening direction through a pushrod 36. When an
electromagnetic solenoid 38 is energized, the pushrod 36 is
attracted in a valve-closing direction of the spill valve 28. The
biasing force of the valve-opening spring 40 is greater than the
biasing force of the valve-closing spring 34. Thus, when the
electromagnetic solenoid 38 is not energized, the spill valve 28 is
opened by the biasing force of the valve-opening spring 40. When
the electromagnetic solenoid 38 is energized, the pushrod 36 is
magnetically attracted against the biasing force of the
valve-opening spring 40. The biasing force of the valve-opening
spring 40 is not transmitted to the spill valve 28 so that the
spill valve 28 is closed by the biasing force of the valve-closing
spring 34. The spill valve 28 is a normally opened valve.
[0023] The plunger 22 has a tappet 42 at its lower end. The tapped
42 is brought into a contact with a pump cam 48 by a spring 44. The
pump cam 48 is driven by a driving shaft 46. The driving shaft 46
is mechanically connected to a camshaft 50. In FIG. 1, the camshaft
50 represents an intake camshaft and an exhaust camshaft. The
camshaft 50 is driven by a crankshaft 52. A rotational speed ratio
between the crankshaft 52 and the camshaft 50 is "1:2". The driving
shaft 46 rotates at half speed of the crankshaft 52. The pump cam
48 has a pump cam profile on its outer periphery. The plunger 22
reciprocates in the cylinder 20 in synchronization with the driving
shaft 46. When the plunger 22 slides down, the volume of the pump
chamber 24 is increased to suction the fuel into the pump chamber
24 (suction stroke). When the plunger 22 slides up, the volume of
the pump chamber 24 is decreased to discharge the fuel from the
pump chamber 24 (discharge stroke).
[0024] When the high-pressure fuel pump 18 is at the suction
stroke, the spill valve 28 is opened to introduce the fuel into the
pump chamber 24 through the inlet port 26. It is preferable that
the electromagnetic solenoid 38 is deenergized to open the spill
valve 28. However, even when the electromagnetic solenoid 38 is
energized, the spill valve 28 can be opened. That is, the fuel
pressure supplied from the feed pump 14 is applied to the spill
valve 28 in the valve-opening direction, and a force generated due
to an increase in the pump chamber volume is exerted on the spill
valve 28 in the valve-opening direction. When these forces become
greater than the biasing force of the valve-closing spring 34, the
spill valve 28 can be opened.
[0025] Even when the high-pressure fuel pump 18 is at the discharge
stroke, if the electromagnetic solenoid 38 is deenergized, the
spill valve 28 is opened. Thus, even when the plunger 22 slides up
in the cylinder 20, the fuel in the pump chamber 24 is returned to
the inlet port 26 through the spill valve 28. Thus, the fuel in the
pump chamber 24 is not pressurized, so that the high-pressure fuel
pump 18 does not discharge the fuel. On the other hand, when the
electromagnetic solenoid 38 is energized, the spill valve 28 is
closed and the fuel in the pump chamber 24 is pressurized by the
plunger 22. When the fuel pressure in the pump chamber 24 exceeds a
valve-opening pressure of the discharge valve 32, the high-pressure
fuel in the pump chamber 24 is discharged to the outlet port 30
through the discharge valve 32.
[0026] A discharge rate of the high-pressure fuel pump 18 can be
adjusted by controlling a valve-closing timing of the spill valve
28 at the discharge stroke. Specifically, an early valve-closing
timing of the spill valve 28 at the discharge stroke increases an
effective stroke of the plunger 22 so that the discharge rate of
the high-pressure fuel pump 18. In other words, as an energization
start timing of the electromagnetic solenoid 38 is made earlier,
the discharge rate of the high-pressure fuel pump 18 becomes
larger.
[0027] The high-pressure fuel discharged from the high-pressure
fuel pump 18 is introduced into a delivery pipe (accumulator) 56
through a high-pressure pipe 54. The delivery pipe 56 accumulates
the high-pressure fuel therein and supplies the high-pressure fuel
to a fuel injector 58 of each cylinder. It should be noted that the
delivery pipe 56 is fluidly connected to the fuel tank 10 through a
relief valve 60 and a relief pipe 62. The relief valve 60 is a
pressure regulator which maintains the pressure in the delivery
pipe 56 within a specified value.
[0028] The fuel injector 58 injects the fuel into a combustion
chamber 64 directly. The injected fuel and an intake air are mixed
and are ignited by a spark plug (not shown). A combustion energy is
converted into a rotation energy of the crankshaft 52.
[0029] A starter 66 is connected to the crankshaft 52. When an
ignition switch 68 is turned on, the starter 66 receives
electricity from a battery 70 so as to crank the crankshaft 52.
[0030] A crank angle sensor 72 is arranged at a vicinity of the
crankshaft 52 for detecting a rotational angle of the crankshaft
52. The crank angle sensor 72 outputs a rectangular crank angle
signal when protrusions provided on a rotor of the crankshaft 52
pass the crank angle sensor 72. The protrusions are arranged at
regular intervals (for example, 6.degree. C.A). It should be noted
that the rotor has no-protrusion portion for performing the
cylinder identification. When this no-protrusion portion passes the
crank angle sensor 72, the crank angle sensor 72 does not output
the crank angle signal.
[0031] A cam angle sensor 74 is arranged at a vicinity of the
camshaft 50 for detecting a rotational angle of the camshaft 52.
The cam angle sensor 74 outputs a rectangular crank angle signal
when protrusions provided on a rotor of the camshaft 50 pass the
cam angle sensor 74. The protrusions are arranged at regular
intervals (for example, 180.degree. C.A). It should be noted that
the rotor of the camshaft 50 has additional protrusions for
performing the cylinder identification.
[0032] An electronic control unit (ECU) 76 controls various
actuators for performing a fuel injection control. The ECU 76
receives detection signals from an accelerator position sensor 78,
a coolant temperature sensor 80, a battery voltage sensor 82, a
fuel pressure sensor 84 detecting the fuel pressure in the delivery
pipe 56, the crank angle sensor 72, and the cam angle sensor 74.
The ECU 76 controls an energization of the electromagnetic solenoid
38 so that the actual fuel pressure in the delivery pipe 56 agrees
with the target fuel pressure.
[0033] FIG. 2 is a block diagram showing a fuel pressure control in
a delivery pipe 56.
[0034] A cylinder identification unit B2 performs a cylinder
identification based on a crank angle signal "Crank" detected by
the crank angle sensor 72 and a cam angle sensor "Cam" detected by
the cam angle sensor 74. In the cylinder identification, the ECU 76
obtains a current rotational angle of the crank shaft 52 in one
combustion cycle (720.degree. C.A) in a case that the rotational
angle of the crankshaft 52 is set as a reference (0.degree. C.A) at
a time when a specified piston is at a top dead center of a
compression stroke. Further, the ECU 76 obtains a current position
of the plunger 22. That is, the ECU 76 determines whether the
high-pressure fuel pump 18 is at the suction stroke or the
discharge stroke.
[0035] An injection quantity computation unit B4 computes a command
fuel injection quantity "QFIN" based on an engine speed represented
by the crank angle signal "Crank" and an accelerator stepped amount
"ACCP" detected by the accelerator position sensor 78.
[0036] A target fuel pressure computation unit B6 computes a target
fuel pressure "PFIN" in the delivery pipe 56 based on the command
fuel injection quantity "QFIN" and the engine speed.
[0037] A feedback control unit B8 computes a discharge rate of the
high-pressure fuel pump 18 (feedback amount), which is necessary
for performing a feedback control in order that the actual fuel
pressure "P" detected by the fuel pressure sensor 84 agrees with
the target fuel pressure "PFIN" Specifically, the feedback amount
is computed by proportional-integral control based on the actual
fuel pressure "P" and the target fuel pressure "PFIN".
[0038] A variation computation unit B10 computes a pressure
variation ".DELTA.PFIN" in the target fuel pressure "PFIN". A
convert unit B12 converts the pressure variation ".DELTA.PFIN" into
a fuel quantity which is necessary for varying the actual fuel
pressure "P" by the pressure variation ".DELTA.PFIN". In this
convert, a coefficient of volumetric expansion "E" of the fuel is
divided by a total volume "V" of the high-pressure pipe 54 and the
delivery pipe 56. The pressure variation ".DELTA.PFIN" is
multiplied by "E/V".
[0039] A feedforward control unit B14 computes a discharge rate of
the high-pressure fuel pump 18 (feedforward amount) which
corresponds to a total quantity of the command fuel injection
quantity "QFIN" and the fuel quantity obtained in the convert unit
B12.
[0040] An addition unit B16 computes a final required discharge
rate of the high-pressure fuel pump 18 by adding together the
feedback amount and the feedforward amount.
[0041] A timing computation unit B18 computes an energization
timing of the electromagnetic solenoid 38, which corresponds to a
valve-closing timing of the spill valve 28, based on the crank
angle signal "Crank" and the above final required discharge rate.
Specifically, the energization timing of the electromagnetic
solenoid 38 is derived from an energization timing map which is
previously obtained by experiment by use of the final required
discharge rate as a parameter. The electromagnetic solenoid 38 is
energized during a specified time period from the energization
timing when the high-pressure fuel pump 18 is at the discharge
stroke.
[0042] A switch unit B20 switches an energization way of the
electromagnetic solenoid 38 based on a determination result of the
cylinder identification unit B2. That is, when it is determined
that the cylinder identification has been completed, it can be
determined whether the high-pressure fuel pump 18 is at the suction
stroke or the discharge stroke. Thus, the electromagnetic solenoid
38 is energized at the energization timing computed by the timing
computation unit B18. This energization of the electromagnetic
solenoid 38 is referred to as a normal-control, hereinafter. The
switch unit B20 electrically connects the timing computation unit
B18 with the electromagnetic solenoid 38.
[0043] On the other hands, when it is determined that the cylinder
identification has not been completed, it can not be determined
whether the high-pressure fuel pump 18 is at the suction stroke or
the discharge stroke. Thus, above described normal-control can not
be performed. The switch unit B20 electrically connects a
start-control unit B22 with the electromagnetic solenoid 38.
[0044] The start-control unit B22 starts to energize the
electromagnetic solenoid 38 continuously in order that the
discharge rate of the high-pressure fuel pump 18 becomes maximum
when the ignition switch 68 is turned on. This processing is for
restricting a deterioration in the exhaust characteristic after the
engine is started. That is, in a case that the engine has been
stopped for a long time period after the ignition switch 68 is
turned off, it is likely that the actual fuel pressure in the
delivery pipe 56 excessively decreases when the engine is
re-started. For example, the fuel pressure in the delivery pipe 56
decreases to atmospheric pressure. The combustion condition after
re-starting engine is deteriorated and the exhaust characteristic
may be deteriorated. Thus, it is required that the actual fuel
pressure is increased to the target fuel pressure immediately after
the engine is re-started. However, until the cylinder
identification is completed, the normal-control can not be
performed. According to the present embodiment, the electromagnetic
solenoid 38 is continuously energized after the ignition switch 68
is turned on until the cylinder identification is completed,
whereby the discharge rate of the high-pressure fuel pump 18 is
made maximum. This energization of the electromagnetic solenoid 38
is referred to as a start-control, hereinafter. In this situation,
a stroke of the high-pressure fuel pump 18 is changed from the
suction stroke to the discharge stroke while the electromagnetic
solenoid 38 is energized, so that the spill valve 28 is closed from
a start timing of the discharge stroke and the discharge rate of
the high-pressure fuel pump 18 can be made maximum. Thus, the
increase in the actual fuel pressure after the re-start of engine
is expedited to restrict the deterioration in the exhaust
characteristic.
[0045] If the actual fuel pressure is excessively low or
excessively high at engine starting, the actual fuel pressure
largely deviates from the target fuel pressure at a completion
timing of the cylinder identification. When the start-control is
terminated at the completion timing of the cylinder identification
and the actual fuel pressure is excessively lower than the target
fuel pressure, the integral term of the feedback control becomes
excessively large, which may cause an overshoot. Also, when the
actual fuel pressure is excessively higher than the target fuel
pressure, an actual completion timing of the start-control is
retarded relative to an appropriate completion timing. If the
actual fuel pressure is excessively higher than the target fuel
pressure at the actual completion timing of the start-control, the
integral term of the feedback control becomes excessively large,
which may cause an undershoot. As described above, if the
start-control is terminated at the completion timing of the
cylinder identification, it is likely that a controllability of the
actual fuel pressure may deteriorate.
[0046] According to the present embodiment, a duration time
computation unit B24 estimates a duration time (start-control
duration time) until a difference between the actual fuel pressure
and the target fuel pressure becomes lower than a specified value.
During this start-control duration time, the start-control is
performed to avoid the deterioration in controllability of the
actual fuel pressure.
[0047] FIG. 3 is a flowchart showing a processing of the
start-control. This process is repeatedly performed at a specified
interval (5 msec) by the ECU 76.
[0048] In step S10, the computer determines whether the engine is
stopped. This process is for determining whether it is a condition
where the high-pressure fuel pump 18 is driven by turning on the
ignition switch 68. It should be noted that the computer determines
whether the engine is stopped based on the crank angle signal
"Crank" and the cam angle signal "Cam".
[0049] When the answer is NO in step S10, that is, when the engine
is not stopped, the procedure proceeds to step S12 in which the
computer determines whether the current processing is a first
processing after the starter 66 is firstly driven by turning on the
ignition switch 68. This process is for determining whether an
engine start requirement is generated.
[0050] When the answer is YES in step S12, the procedure proceeds
to step S14 in which the actual fuel pressure at engine starting is
detected by the fuel pressure sensor 84.
[0051] In step S16, the computer sets a start-control duration
time. It should be noted that the start-control duration time is
quantified based on the number of output of the crank angle signal
from the crank angle sensor 72 after the starter 66 is started.
That is, the number of output of the crank angle signal until the
actual fuel pressure "P" is increased to the target fuel pressure
"PFIN" is defined as the start-control duration time. The discharge
stroke of the high-pressure fuel pump 18 corresponds to the
rotational angle of the crank shaft 52. The number of discharge of
the high-pressure fuel pump fuel 18 which is required to increase
the actual fuel pressure "P" to the target fuel pressure "PFIN" can
be converted into the number of output of the crank angle signal.
It should be noted that the maximum discharge rate of the
high-pressure fuel pump 18 per one discharge stroke and an
increment in the actual fuel pressure by one maximum discharge rate
of the high-pressure fuel pump 18 depend on specifications of the
high-pressure fuel pump 18, the delivery pipe 56 and the like.
Thus, based on these specifications, the number of discharge
(discharge stroke) of the high-pressure fuel pump 18 necessary for
increasing the actual fuel pressure "P" to the target fuel pressure
"PFIN" can be computed. Specifically, the total volume "V" of the
high-pressure pipe 54 and the delivery pipe 56 is divided by the
coefficient of volumetric expansion "E" of the fuel. The maximum
discharge rate of the high-pressure fuel pump 18 is multiplied by
"V/E" to obtain an increase in the actual fuel pressure due to one
fuel discharge of the high-pressure fuel pump 18 at the maximum
discharge rate. Then, the difference pressure between the fuel
pressure at engine starting and the target fuel pressure "PFIN" is
divided by the above increase in the actual fuel pressure to obtain
the number of discharge of the high-pressure fuel pump 18.
[0052] In step S18, a guard process of the start-control duration
time is executed. In this guard process, an upper guard and a lower
guard are set to the start-control duration time. The upper guard
is set in order to avoid a situation in which the reliability of
the fuel pump 18 deteriorates due to a heat generation in the
electromagnetic solenoid 38 when the energization of the
electromagnetic solenoid 38 has been continuously energized for a
long period. Also, the lower guard is set to ensure one discharge
stroke of the high-pressure fuel pump 18 at the maximum discharge
rate even if the difference between the actual fuel pressure at
engine starting and the target fuel pressure "PFIN" is excessively
small and a fuel quantity necessary for increasing the actual fuel
pressure "P" to the target fuel pressure "PFIN" is excessively
small. These upper and lower guards are set for performing an
abnormality diagnosis which will be described later.
[0053] After the process in step S18 is completed, or when the
answer is NO in step S12, the procedure proceeds to step S20 in
which the computer determines whether current process is executing
within the start-control duration time. This determination is
executed based on whether the number of output of the crank angle
signal "Crank" after the starter 66 is started until the current
process is executed is equal to the number of output of the crank
angle signal obtained in step S16.
[0054] When the answer is YES in step S20, the procedure proceeds
to step S22 in which the switch unit B20 electrically connects the
start-control unit B22 with the electromagnetic solenoid 38.
[0055] When the answer is NO in step S20, the procedure proceeds to
step S24 in which the computer determines whether a diagnosis
completion flag "F" is set to "1". This process is for determining
whether a diagnosis of a fuel system has been performed. When the
diagnosis completion flag "F" is "0", it means that the diagnosis
has not been performed. When the diagnosis completion flag "F" is
"1", it means that the diagnosis has been performed.
[0056] When the answer is NO in step S24, the procedure proceeds to
step S26 in which the diagnosis is performed. In this diagnosis
process, it is diagnosed whether a defect exists in the fuel supply
pipe between the fuel tank 10 and the fuel injector 58, the fuel
injector 58 and the fuel pressure sensor 84. According to the
present embodiment, the diagnosis is performed based on whether the
variation in the actual fuel pressure "P" during the start-control
duration time is within a specified range. If a fuel leakage occurs
in the low-pressure pipe 12, the feed pump 14, the high-pressure
fuel pump 18, the high-pressure pipe 54, the fuel injector 58 and
the like, or if the fuel pressure sensor 84 has a malfunction, the
variation in the actual fuel pressure "P" deviates from the
specified range. When the diagnosis has been performed, the
diagnosis completion flag "F" is set to "1". If it is diagnosed
that a defect exists, an engine check lump (not shown) is lighted
to notify a driver of a defect.
[0057] When the process in step S26 is completed, or when the
answer is YES in step S24, the procedure proceeds to step S28 in
which the switch unit B20 electrically connects the timing
computation unit B18 with the electromagnetic solenoid 38.
[0058] When the answer is YES in step S10, or when the processes in
steps S22, S28 are completed, the processing is terminated.
[0059] FIGS. 4A to 4C are time charts showing an energization
operation of the electromagnetic solenoid 38 according to the
start-control. Specifically, FIG. 4A shows ON-OFF condition of the
starter 66, FIG. 4B shows ON-OFF condition of the electromagnetic
solenoid 38, and FIG. 4C shows a variation in the actual fuel
pressure "P".
[0060] When the ignition switch 68 is tuned on and the starter 66
is started at a time "t1", the start-control is started and is
continued until the number of the output of the crank angle signal
"Crank" reaches a specified number necessary for increasing the
actual fuel pressure "P" to the target fuel pressure "PFIN". That
is, the electromagnetic solenoid 38 is continuously energized. In
FIGS. 4B and 4C, solid lines represent ON-OFF condition of the
electromagnetic solenoid 38 and the variation in the actual fuel
pressure "P" in a case that the fuel pressure at engine starting is
decreased to atmospheric pressure. Dotted lines represent those in
a case that the fuel pressure at engine starting is relatively
high. In a case that the fuel pressure at engine starting is
decreased to atmospheric pressure, the start-control is performed
during a period from a time "t1" to a time 14''. In a case that the
fuel pressure at engine starting is relatively high, the
start-control is performed during a period from a time "t1" to a
time "t3". Thus, the completion timing of the start-control can be
set to an appropriate timing so that a difference between the
actual fuel pressure "P" and the target fuel pressure "PFIN" is
made as small as possible.
[0061] According to the above mentioned embodiment, following
advantages can be obtained.
[0062] (1) The start-control duration time is set at starting of
the starter 66, and the start-control is performed during this
start-control duration time. Thereby, the difference between the
actual fuel pressure "P" and the target fuel pressure "PFIN" is
made as small as possible, so that an increase in the integral term
of the feedback control is restricted and a deterioration in the
controllability of the actual fuel pressure can be avoided.
[0063] (2) The start-control duration time is quantified based on
the number of output of the crank angle signal "Crank" from the
crank angle sensor 72. Thus, the completion timing of the
start-control can be accurately and easily obtained.
[0064] (3) The upper guard of the start-control duration time is
established. Thus, it can be avoided that the reliability of the
fuel pump 18 deteriorates due to a heat generation in the
electromagnetic solenoid 38 when the energization of the
electromagnetic solenoid 38 has been continuously energized for a
long period.
[0065] (4) The lower guard of the start-control duration time is
established. Thus, a diagnosis can be performed immediately after
the engine is started.
Second Embodiment
[0066] A second embodiment will be described hereinafter, focusing
on a difference from the first embodiment.
[0067] According to the second embodiment, in the start-control
duration time, an energization period of the electromagnetic
solenoid 38 is made short based on the crank angle signal "Crank"
and the cam angle signal "Cam". When the high-pressure fuel pump 18
is at the discharge stroke, the spill valve 28 is closed to
discharge the high-pressure fuel. Even if the electromagnetic
solenoid 38 is deenergized after the fuel discharge is started, the
pressure in the pump chamber 24 is high enough to maintain the
spill valve 28 closed. The fuel discharge is continued. Thus, after
the spill valve 28 is closed by energizing the electromagnetic
solenoid 38 at a start timing of the discharge stroke, the
discharge rate of the high-pressure fuel pump 18 can be made
maximum without respect to the energization of the electromagnetic
solenoid 38.
[0068] Specifically, according to the present embodiment, a
protrusion is provided on the rotor of the cam shaft 50 at an
advanced position relative to the discharge stroke. The
electromagnetic solenoid 38 is energized during a specified angle
range including a start point of the discharge stroke after the
protrusion is detected by the cam angle sensor 74. Thus, it can be
avoided that the electromagnetic solenoid 38 is continuously
energized before a stroke identification.
[0069] FIGS. 5A to 5F are time charts showing an energization
operation of the electromagnetic solenoid 38 according to the
start-control. Specifically, FIG. 5A shows ON-OFF condition of the
starter 66, FIG. 5B shows a crank angle signal "Crank", FIG. 5C
shows a cam angle signal "Cam", FIG. 5D shows ON-OFF condition of
the electromagnetic solenoid 38, FIG. 5E shows a position of a
plunger 22, and FIG. 5F shows a variation in the actual fuel
pressure "P". The output interval of the crank angle signal "Crank"
is 6.degree. C.A. However, in FIG. 5B, the output interval is
indicated as 12.degree. C.A.
[0070] When the starter 66 is started at a time "t1", the
start-control duration time is set. The electromagnetic solenoid 38
is energized from a time "t2" until a time "t4". At the time "t2",
the cam angle signal "Cam" is outputted. The time "t4" corresponds
to an end time of the specified angle range. Thereby, the stroke of
the high-pressure fuel pump 18 is changed from the suction stroke
to the discharge stroke, and the spill valve 28 is closed at a time
"t3". The high-pressure fuel pump 18 continues to discharge fuel
from the time "t3" until a time "t5". Similarly, the
electromagnetic solenoid 38 is energized from a time "t6" until a
time "t7", from a time "t8" until a time "t9", and from a time
"t10" until a time "t11" so that the discharge rate of the
high-pressure fuel pump 18 can be made maximum during the
start-control duration time.
[0071] In FIGS. 5D and 5F, solid lines represent ON-OFF condition
of the electromagnetic solenoid 38 and the variation in the actual
fuel pressure "P" in a case that the fuel pressure at engine
starting is decreased to atmospheric pressure. Dotted lines
represent those in a case that the fuel pressure at engine starting
is relatively high.
[0072] As described above, according to the present embodiment, the
energization period of the electromagnetic solenoid 38 in the
start-control duration time can be made short, and the electric
power consumption of the electromagnetic solenoid 38 can be
reduced. Further, it can be avoided that the reliability of the
fuel pump 18 deteriorates due to a heat generation in the
electromagnetic solenoid 38.
Third Embodiment
[0073] A third embodiment will be described hereinafter, focusing
on a difference from the first embodiment.
[0074] In the third embodiment, the spill valve 28 of the
high-pressure fuel pump 18 is a normally close valve. That is, when
the electromagnetic solenoid 38 is not energized, the spill valve
28 is closed. When the electromagnetic solenoid 38 is energized,
the spill valve 28 is opened. By controlling a close timing of the
spill valve 28 at the discharge stroke of the high-pressure pump
18, the discharge rate of the high-pressure fuel pump 18 is
adjusted.
[0075] FIGS. 6A to 6C are time charts showing an energization
operation of the electromagnetic solenoid 38 according to the
start-control, and correspond to FIGS. 4A to 4C. FIG. 6C shows a
case in which the fuel pressure at engine starting is decreased to
atmospheric pressure.
[0076] The starter 66 is started at a time "t1". During the
start-control duration time from the time "t1" until a time "t3",
the electromagnetic solenoid 38 is continuously deenergized, so
that the discharge rate of the high-pressure fuel pump 18 is made
maximum. After the start-control duration time has passed, the
normal-control is performed.
Fourth Embodiment
[0077] A fourth embodiment will be described hereinafter, focusing
on a difference from the first embodiment.
[0078] FIG. 7 is a block diagram showing a fuel pressure control in
a delivery pipe 56. In the present embodiment, the start-control
duration time is established based on a fuel quantity (number of
discharge stroke of the high-pressure fuel pump 18) necessary for
increasing the actual fuel pressure "P" to the target fuel pressure
"PFIN". It should be noted that the duration time computation unit
B24 computes the start-control duration time based on a battery
voltage "VB" detected by a battery sensor 82 and a coolant
temperature "THW" detected by a coolant temperature sensor 80 in
addition to the fuel pressure at engine starting and the target
fuel pressure "PFIN". If the battery voltage "VB" is low, the
rotational speed of the starter 66 is decreased and a cranking
speed is also decreased. Also, if the coolant temperature "THW" is
low, a viscosity of lubricant is increased and the cranking speed
is decreased. In these cases, the discharge rate of the
high-pressure fuel pump 18 may vary and the difference between the
actual fuel pressure "P" and the target fuel pressure "PFIN" may be
increased when the start-control duration time has passed.
According to the present embodiment, since the start-control
duration time is established based on the battery voltage "VB" and
the coolant temperature "THW", the start-control duration time can
be established with high accuracy.
[0079] It should be noted that the start-control duration time is
computed based on the actual fuel pressure "P" and the target fuel
pressure "PFIN", and then the start-control duration time is
corrected by the battery voltage "VB" and the coolant temperature
"THW". Alternatively, the start-control duration time can be
derived from a four-dimensional map of the actual fuel pressure
"P", the target fuel pressure "PFIN", the battery voltage "VB" and
the coolant temperature "THW".
Other Embodiments
[0080] The above-mentioned embodiments may be modified as follows:
[0081] In the first embodiment, a processing interval of the ECU 76
is set to a specified period (5 msec). However, the processing
interval of the ECU 76 can be set to an output interval of the cam
angle signal "Cam". When the engine speed is increased, the output
interval of the cam angle signal "Cam" becomes short, which may
increase a computation load of the ECU 76. For this reason, when
the engine speed is lower than or equal to a specified value, the
processing interval of the ECU 76 is set to the output interval of
the cam angle signal "Cam". When the engine speed is lower than the
specified value, the processing interval of the ECU 76 is set to
the specified period (5 msec). [0082] In the above first
embodiment, the start-control duration time is set based on the
number of output of the crank angle signal "Crank". Alternatively,
the start-control duration time can be set based on the number of
output of the cam angle signal "Cam". [0083] The fuel pressure at
engine starting can be estimated based on the fuel pressure at
engine stopping and an elapsed time from previous engine stopping
until current engine starting. [0084] The feedback control at
normal-control may not include the integral term. [0085] In the
fourth embodiment, the start-control duration time is established
based on parameters including the battery voltage "VB" and the
coolant temperature "THW". However, the start-control duration time
can be established based on parameters including one of the battery
voltage "VB" and the coolant temperature "THW". The coolant
temperature "THW" can be replaced by a fuel temperature. [0086] In
the above embodiments, when the engine is stopped, the plunger 22
of the high-pressure fuel pump 18 may be controlled to be
positioned at a bottom dead center. Thus, when starting the starter
66, the position of the plunger 22 can be detected to obtain the
discharge rate of the high-pressure fuel pump 18 with high
accuracy. The accuracy of estimating the start-control duration
time can be more improved.
[0087] The start-control duration time can be prolonged if the
actual fuel pressure "P" does not reach the target fuel pressure
"PFIN" at a specified timing. Further, the start-control duration
time can be renewed at a specified timing. [0088] In the above
embodiments, the discharge rate of the high-pressure fuel pump can
be established by feedback control. [0089] In the second
embodiment, the electromagnetic solenoid 38 can be continuously
energized before the cam angle signal "Cam" is inputted or the
stroke identification of the high-pressure fuel pump 18 is
performed. This energization period of the electromagnetic solenoid
38 can include a start timing of the discharge stroke of the
high-pressure fuel pump. [0090] In the above embodiments, one cycle
of the discharge stroke and the suction stroke is not limited to
180.degree. C.A.
[0091] The present invention can be applied to a diesel engine as
well as a gasoline engine.
* * * * *